Quaternary ammonium compounds (quats), and particularly didecyldimethylammonium chloride (DDAC) ##STR3## are commonly used as wood preservatives because they possess resistance properties to fungi and termites, to loss of strength, and to electrical sensitivity similar to those of commonly used acidic copper/chromium/arsenic solution (CCA) or ammoniacal copper and arsenic salt solution preservatives. See Proc of the Am. Wood Pres. Assoc., 80:191-210 (1984). Although chloride quats do not include potentially dangerous heavy metals, didecyldimethylammonium chloride leaches rapidly in soil (Nicholas et al., Forest Prod. J., 41:41 (1991), and therefore, does require coupling with copper salt.
Findlay et al., U.S. Pat. No. 4,929,454, disclose a method of preserving wood by impregnation with a quaternary ammonium compound and at least one of zinc and copper, wherein the quat anion is chosen from the group consisting of hydroxide, chloride, bromide, nitrate, bisulfate, acetate, bicarbonate, and carbonate, formate, borate and fatty acids. These quats have distinct environmental and safety advantages over commonly used acidic copper/chromium/arsenic solution (CCA) or ammoniacal copper and arsenic salt solution preservatives in that potentially dangerous heavy metals are not included. The Findlay et al. quats require copper or zinc in order to render them relatively insoluble and to prevent them from leaching out of a treated substrate. The use of copper or zinc in the above formulations may yet raise environmental and corrosion concerns.
Additionally, didecyldimethylammonium chloride tends to absorb preferentially to the surface of the wood and does not uniformly treat the whole substrate. Finally, DDAC treated wood shows a surface erosion or ages upon exposure to light. See Preston et al., Proc. Am. Wood Pres. Assoc., 83:331 (1987).
The biocidal activities of various chloride quats against bacteria, fungi, and algae are tabulated in Cationic Surfactants, E. Jungerman Ed., pp. 56-57, Marcel Dekker, Inc., 1969. Nicholas, "Interaction of Preservatives with Wood," Chemistry of Solid Wood, Advances in Chemistry Series #207, Powell ed., (A.C.S. 1984), notes that didecyldimethylammonium compounds and particularly DDAC are potential biocides. Preston, J.A.O.C.S. 60:567 (1983), concurs and suggests that maximum fungitoxicity is exhibited with dialkyldimethyl compounds having C.sub.10 -C.sub.12 alkyl groups. Butcher et al., Chem Abstracts No. 91:152627b, suggest that the presence of an acid or a base can affect the activity of didecyldimethylammonium quats.
Didecyldimethylammonium acetate was used as a phase transfer catalyst for an oxidation in Chem Abstracts No. 97:9175. A wood preservative was prepared by autoclaving didecylmethylamine with gluconic acid and ethylene oxide in isopropanol to yield (C.sub.10 H.sub.21).sub.2 CH.sub.3 N ((CH.sub.2).sub.2 O).sup.+ gluconate.sup.- in Chem Abstracts No. 109:124403x, while disinfectant solutions were prepared by exchanging a benzylammonium chloride with a chlorhexidene gluconate in Chem Abstracts No. 103:109954f.
Microbiocidal compositions which include quaternary ammonium compounds of the formula R.sup.1 N.sup.+ R.sup.2 R.sup.3 R.sup.4 X.sup.-, wherein at least one of R.sup.1, R.sup.2, or R.sup.3 is a C.sub.8 -C.sub.30 alkyl or alkenyl group and the remainder of R.sup.1, R.sup.2 or R.sup.3 is methyl, ethyl, CH.sub.2 Ph or 4-pyridylmethyl; R.sup.4 is methyl or ethyl; and X is an anion of an acid having a C.sub.7 or greater hydrophobic group, were disclosed in Chem Abstracts Nos. 113:154360f and 113:153776j. Chem Abstracts No. 112:79768u discloses compounds of the formula R.sup.1 R.sup.2 R.sup.3 N.sup.4 N.sup.+ X.sup.-, wherein R.sup.1, R.sup.2, and R.sup.3 are methyl, ethyl, benzoyl, 4-pyridinomethyl and at least one is C.sub.8 -C.sub.30 alkyl or alkenyl; R.sup.4 is methyl or ethyl; and X is a counter anion of acids having C.sub.7 or greater hydrophobic groups. Dimethyldidecylammonium dodecylbenzenesulfonate was demonstrated to impart long term rot resistance to wood without causing rust, while the chloride salts of similar compounds were demonstrated to cause rust.
Patton et al., U.S. Pat. No. 5,004,760, disclose polymeric foams incorporating various dialkyldimethylammonium carboxylates such as didecyldimethylammonium poly(ethylene/acetate) and the like.
Quaternary ammonium compounds (quats) are typically prepared by the reaction: EQU R.sup.1 R.sup.2 R.sup.3 N+R.sup.4 X.fwdarw.R.sup.1 R.sup.2 R.sup.3 R.sup.4 NX (II)
wherein X is a halogen, a sulfate, a sulfo compound, or the like. When at least one of R.sup.1, R.sup.2, R.sup.3, or R.sup.4 is C.sub.12 or longer, the product is an inert soap. Many of the inert soaps have biocidal activity against bacteria, fungi, algae, and related organisms.
Reaction (II) above is limited by the reactant R.sup.4 X because R.sup.4 must react with tertiary amines. For example, methyl chloride (R.sup.4 X.dbd.CH.sub.3 Cl) will react with a tertiary amine at less than 100.degree. C. to yield a quaternary compound R.sub.3 N.sup.+ CH.sub.3 Cl.sup.-, while methanol or methyl acetate (R.sup.4 X.dbd.CH.sub.3 OH or CH.sub.3 COOCH.sub.3) will not, under similar reaction conditions.
General quaternary ammonium compounds with a sulfo group are easily prepared either by the reaction of a sulfate compound with a tertiary amine (III) or by a double exchange (IV). EQU R.sub.3 N+RSO.sub.3 CH.sub.3 .fwdarw.R.sub.3 NCH.sub.3.sup.+ RSO.sub.3.sup.-(III) EQU R.sub.3 N.sup.+ CH.sub.3 Cl.sup.- +RSO.sub.3.sup.- Na.sup.+ .fwdarw.R.sub.3 NCH.sub.3.sup.+ RSO.sub.3.sup.- +NaCl (IV)
If trimethylamine is heated with carbon dioxide and methanol above 200.degree. C. and at 85 to 95 atmospheres, the carbonate quat, bis-tetramethylammonium carbonate, is prepared. Industrial Organic Nitrogen Compounds, Astle Ed. p 66, Reinhold Inc, 1961. However, this reaction is limited to the methyl compound because higher homologs decompose to olefins by the Hofman elimination reaction. See, Organic Reactions, 11, Chptr. 5, 377, Krieger Publishing Co., 1975.
Chem Abstracts 110:212114 (1989) suggests that dimethyl carbonate will react with triethylamine in methanol in twelve hours at 115.degree. C. and under pressure to yield a methyl carbonate ester quat.
Chem Abstracts 114:24824 (1991) discloses that 6-hydroxylhexyldimethylamine reacts with dimethyl carbonate to yield a carbonate ester quat.
Quaternary ammonium hydroxides (hydroxy quats), an intermediate in the reaction scheme of the present invention, are currently prepared by the reaction of quaternary ammonium iodide with silver oxide (V). EQU RN.sup.+ (CH.sub.3).sub.3 I.sup.- +AgO.fwdarw.RN.sup.+ (CH.sub.3).sub.3 OH.sup.- +AgI (V)
However, this reaction is costly, and it is difficult to recover the silver reagent. See, Organic Reactions, 11:Chptr 5, pp. 376-377, Krieger Publishing Co., 1975.
In an olefin synthesis, it has been suggested to treat a quaternary salt with aqueous sodium or potassium followed by pyrolysis in order to form the hydroxy quat and then to decompose the hydroxy quat directly. However, in this method the hydroxy quat is not isolated and the conditions for its preparation are undesirable. See, Organic Reactions, 11:Chptr 5, pp. 376-377, Krieger Publishing Co., 1975.
Talmon et al., Science, 221, 1047 (1983), have used an ion exchange resin to convert didecyldimethylammonium bromide to didecyldimethylammonium hydroxide (VI). EQU (C.sub.12 H.sub.25).sub.2 (CH.sub.3).sub.2 N.sup.+ Br.sup.- +Ion Exchange Resin.fwdarw.(C.sub.12 H.sub.25).sub.2 (CH.sub.3).sub.2 N.sup.+ OH.sup.-(VI)
However, 50 ml of ion exchange resin and two treatment steps were required to convert 3 grams of quaternary ammonium chloride to the corresponding hydroxide. Talmon et al. state that the hydroxy quat can be reacted with acids to make quats with different anions, and they have prepared didodecyldimethylammonium (DDDA) acetate, DDDA-formate, DDDA-propionate, DDDA-butyrate, DDDA-oxalate, DDDA-acrylate, DDDA-tartrate, DDDA-benzoate, and DDDA-octanoate. See also, Organic Synthesis, Collective Volume VI, 552, John Wiley Inc., 1988; Brady et al., J. Am. Chem. Soc., 106:4280-4282, 1984; Brady et al., J. Phys. Chem., 90:9, 1853-1859, 1986; Miller et al., J. Phys. Chem, 91:1, 323-325, 1989; Radlinske et al., Colloids and Surfaces, 46:213-230, 1990.
Distearyldimethylammonium gluconate was prepared via ion exchange and subsequent reaction with an organic acid in Chem Abstracts No. 75:119170U. Miller et al, Langmuir, 4:1363 (1988) prepared ditetradecyldimethylammonium acetate by ion exchange from a bromide.
Alternatively, quaternary ammonium hydroxide compositions have been prepared by treating a haloquat in an electrochemical cell with special cation exchange diaphragms between the cells. The hydroxy quat collects at one electrode, and the halide collects at the other. Hydroxy quats, R.sup.1 R.sup.2 R.sup.3 R.sup.4 N.sup.+ OH.sup.-, wherein the R groups were C.sub.1 -C.sub.4, were treated with carboxylic acids to make asymmetric quats that were used as capacitor driving electrolytes. See, Japanese Patent Publication No. 02-106,915 and Awata et al., Chemistry, Letters., 371 (1985). Awata et al. placed carboxylic acids in the cathode cell to react with tetraethylammonium hydroxide as it was formed.
Japanese Patent Publication No. 01-172,363 discloses the preparation of relatively low yields of tetraethylammonium hydroxide by reacting triethylamine with diethyl sulfate, heating the resultant quat with sulfuric acid to yield the sulfate quat, and reacting the sulfate quat with barium hydroxide to yield the short chain quat, tetraethylammonium hydroxide, and barium sulfate.
Di C.sub.8 -C.sub.12 alkyl quaternary ammonium hydroxides prepared by ion exchange were used as strong bases to digest animal tissue by Bush et al., French Patent Publication No. 1,518,427.
Akzo discloses that the addition of a metallic hydroxide to a quaternary ammonium chloride such as didecyldimethylammonium chloride, in an aqueous medium, results in an equilibrium mixture of quaternary ammonium chloride and quaternary ammonium hydroxide (VII). This reaction can be driven to the right by the use of isopropanol as a solvent. EQU (R.sub.4 N)Cl+KOH.revreaction.(R.sub.4 N)OH+KCl (VII)
Akzo further discloses that the addition of a soap to a quaternary ammonium chloride yields a quaternary ammonium carboxylate (VIII). EQU (R.sub.4 N)Cl+R.sup.1 COONa.fwdarw.(R.sub.4 N) (OOCR.sup.1)+NaCl(VIII)
Jordan et al., U.S. Pat. No. 3,281,458, disclose the preparation of dioctadecyldimethylammonium humate, ditallowdimethylammonium humate, dipentadecyldimethylammonium humate, and didodecyldimethylammonium humate by reacting humic acid, lignite, aqueous sodium hydroxide and a chloride quat.
Finally, Nakama et al., J.A.C.O.S., 67:717 (1990) report the interaction between anionic and cationic surfactant and particularly sodium laureate and stearyltrimethylammonium chloride, while Linderborg, U.S. Pat. No. 4,585,795, disclose the use of synergistic mixtures of the alkali metal salt of certain biocidal organic acids, quaternary ammonium chlorides, and alkyl-pyridinium chlorides as control agents for short-term protection of timber against sapstain fungi and mildew.
It has now been discovered that di C.sub.8 -C.sub.12 alkyl quaternary ammonium carboxylates and/or borates can be incorporated into metal-free wood preservative systems. C.sub.1 -C.sub.20 alkyl or aryl-substituted alkyl, C.sub.8 -C.sub.20 alkyl carboxylate quats, and particularly the di C.sub.8 -C.sub.12 alkyl carboxylate quats above, can be prepared by various methods from C.sub.1 -C.sub.20 alkyl or aryl-substituted alkyl, C.sub.8 -C.sub.20 alkyl quaternary ammonium chloride (chloride quat(s)) starting materials, including by indirect synthesis through C.sub.1 -C.sub.20 alkyl or aryl-substituted alkyl, C.sub.8 -C.sub.20 alkyl quaternary ammonium hydroxide and C.sub.1 -C.sub.20 alkyl or aryl-substituted alkyl, C.sub.8 -C.sub.20 alkyl quaternary ammonium carbonate intermediates or by direct synthesis. C.sub.1 -C.sub.20 alkyl or aryl-substituted alkyl, C.sub.8 -C.sub.20 alkyl borate quats, and particularly the di C.sub.8 -C.sub.12 alkyl borate quats above can be prepared by various methods from C.sub.1 -C.sub.20 alkyl or aryl-substituted alkyl, C.sub.8 -C.sub.20 alkyl quaternary ammonium hydroxide starting materials, which may be prepared as above from the corresponding chloride quats. The di C.sub.8 -C.sub.12 alkyl carbonate and/or borate quats, including those prepared by the methods above, are useful as wood preservatives, as they have improved leaching resistance, particularly without the use of the commonly used metal stabilizers or couplers, arsenic, chromium, copper, and zinc or combinations thereof.